Gold alloy



Patented oa s, .1929

UNITED STATES PATENT OFFICE VICTOR 1). nA'vrenon, ATTLnnono,MASSACHUSETTS, ASSIGNOR To GENERAL PLATE COMPANY, or ATTLEBORO,MASSACHUSETTS, A' CORPORATION on nnonn ISLAND GOLD ALLoY Ho Drawing.Application filed June 10,

The invention relates to alloys of precious metals, and particularly toalloys of gold con taining metals of lowspecific gravity, and to theprocess ofmaking the same.

The gold alloy now commonly used in the. arts has as its characteristicconstituents gold and copper or gold and silver with approprireducingofthe specific gravity .ate base metals other than copper or silver toimpart requisite hardness, color, and other desired properties. Thisalloy, although malleable and ductile to a degree permitting working byusual mill processes of rolling and drawing, has the disadvantage ofpossessing a relatively high specific gravity, present invention hasamong itsob ects the of such alloys by incorporating therein asufficient quantity of low specific'gravity metal or metals such ascalcium, lithium, -magnesium, sil1- con, titanium, and aluminum formaterially reducing the specific gravity of the alloy.

It will be understood that small percentages of metals of low specificgravities in the order of the specific gravities of the metals mentionedabove will materially reducethe specific gravity of the gold alloy,which can be appreciated from an observation'that in a 14: carat goldalloy containing by weight 1 .part magnesium out of 24parts alloy themagnesium will have a volume about 80% that of the gold. v

I have found that magnesium, calcium, lithium, and other metals ofsimilar characteristics cannot be alloyed with gold by usual processes,and that the mixture of raw metals to be compounded to make the alloy,particularly when magnesium is-present, is explosive upon application ofheat sufficient to raise the temperature of the mixture to a valuenecessary to melt the old. These effects I explain are due to the actthat'such 7 low specific gravity metals are highly volatile attemperatures much below that at which gold melts, and consequently willbe destroyed the destruction being aided by the strong aiiinity of themetals for oxygen;

According'to the practice of the improved process the low specificgravity metal is first alloyed with a metal or metals with which it andthe 1926. Serial a. 115,114.

will combine without being destroyed, the resulting alloy then beingalloyed with the gold or with a gold alloy. Preferably, but notnecessarily, the low specific gravity metal is alloyed with a metalwhich has a melting point lessthan that of the low specific gravitymetal, so that the latter will be combmed at of the melting point of thelow specificgravity metal and that of the gold, with the result that thefinal alloy maybe produced without at any time subjecting the raw lowspecific gravity metal or the alloy containing it to an unnecessarilyhigh temperature.

As an example of the practice of the invention, but without limitationthereto, apreliminary alloy consisting of by weight about 2 magnesium,30% zinc, and 50% silver may be made byplacing the raw metals in acrucible and raising their temperature to about 1400 degrees Fahrenheit,with use of suitable fluxes as hereinafter described. I have found thatthe zinc melts first and aparently causes the magnesium to melt into itat a temperature lower than that of the melting point of raw magnesium,and the silver to melt into the liquid. zinc and magnesium at atemperature lower than that of the melting point of silver, the zinctherefore acting to reduce the melting point of the silver andmagnesium. The silver makes the alloyv more homogeneous and raises itsmeltalloys, of which examples are given above,

are in the nature of chemical combinations, being brittle as glass, thesilver alloys meltlng at about 1400 degrees F ahrenhelt. These alloyshave the property of causing gold when metal. For example, if the alloyto be pro-- mixed with the alloy to melt at a temperature of about 1600degrees Fahrenheit, which is lower than the melting point of gold.

In making the preliminaryv alloy the metals may be placed in thecrucible inlump, shot, bar, or sheet form in the inverse order of theirspecific gravities, that is to say the low specific gravity metal in thebottom of the crucible and the metals of higher specific gravity aboveit, so that the low specific gravity metal upon melting tends to risethrough the metals of high specific gravity.

I have found as suitable for flux in preparing the preliminary alloypotassium bifluoride or calcium chloride, or a mixture of the two in theproportion of 1 part calcium chloride and 2 parts potassium bifluoride,cryolite, potassium chloride, sodium chloride, and sodium fluoride. Theflux preferably is placed in the cruciblein crystalline or pow- 'deredform ontop of the metals before heat is applied, sufficient flux beingemployed to maintain upon the molten metals a layer about A inch thick.The contents of the crucible together with'the flux and slag are pouredsimultaneously in a thin stream into the mold so at all times to protectthe molten metal from the action of the air. I have found that this fluxeflectively will eliminate all oxides of the metals entering into thealloy, which oxides if present in the final alloy will render itunhomogeneous. It will be understood that the invention is not limitedto use of the'fiuxes given, but that other fluxes, which will eliminatethe oxides of the low specific gravity metal and form a liquid sealpreventing access of air to the molten metal, may be employed.

The gold preferably is alloyed with the remaining constituents of thefinal alloy prior to being allo ed with the preliminary alloy containingt e volatile low specific v gravity 'duced is'to contain gold, copper,silver and magnesium, the gold may be first alloyed with the copper andsome'of the silver, and the magnesium isfirst alloyed withthe zinc andbalance of the silver, both of these alloys as heretofore explainedhaving ,a melting" point less than that ofgolde'. These two alloys arethen placed in a crucible andlmelted.

remainder copper, or if ium up to 1%, Thespecific gravltyof the alloy tobe pro-= duced may be further reduced by incorporating other lowspecific gravity metals, as for example aluminum which is notparticularly volatile, in which case the aluminum will be preliminarilyalloyed with the gold and copper, as for example by practice of themethod described in United States Patent 1,557,431 granted to me October13, 1925.

In making the final alloy the preliminary alloy containing the volatilelow specific gravity metal may be placed at the bottom of the crucibleand'the alloy containing the gold on top of it, the two alloys being inrelatively small pieces. with a layer about inch thick of suitable fluxand the crucible is placed in a furnace and raised to 1600 degreesFahrenheit, at which temperature the metals become liquid. More flux isthen placed in the crucible, say

"about 1 ounce for each hundred troy ounces of metal, and thetemperature is raised to about 1700 degrees, at which temperature thecrucible is removed from the furnace and the contents thereof are pouredin a thin stream into the mold, which mold may have an elongatedvertically inclined mold chamber of the type'dcscribed in-my aforesaidatent.

As suitable fluxes for making the nal alloy I may use those describedabove in connection with the preliminary alloy. In addition I have alsofound as suitable for use granular sodium chloride, window glass, greenbottle glass, mercury bichloride, and potassium cyanide, all of which.will dissolve or otherwise eliminate the oxides of the low specificgravity metals. I have found that a mixture of sodium chloride, 12%%potassium flu- -metalssuch as silicon and titanium if desired also maybe alloyed with gold'by the above described metho As an example of adesirable 14; carat com mercial green gold alloy the "same may con sistof about 58% .gold, 25% silver, 3% magnesium, 5% zinc, with theremainder copper, or if desired somejof the copper may be substituted byaluminum, for example to make the alloy contain 3% aluminum. As anexample of a desirable commercial 14 carat yellow gold alloy the'alloymay consist of about 58%gold, 3% magnesium, 5% zinc, with the desiredsome of the copper may be replaced by aluminum, for ex ample enough tomake the alloy contain 3% aluminum. 5

I have found that by practice of'the above method calcium-in amounts upto 0.5%, lithand magnesium up to 3% readily maybe incorporated into thealloy.

The metals are then covered By exercise of care it is possible to raisethe calcium content up to 2%, the lithium up to 3%, and the magnesium upto 5%.

My improved alloy is distinguished from h prior alloys in that itcontains 10W specific gravity metals, particularly highly volatileearthy metals in amount-sufficient materially to'reduce its specificgravity, While at the same time it is sufiiciently malleable and ductileto permit working thereof by the usual mill processes of alternateattenuation and an-v nealing, the ingot being sufficiently homogeneousand free from checks and blisters to permit economic utilizationthereof. 1

Although I have described several examples of alloys and metals for usetherein, one example of the improved method and several examples offluxes for use therewith, it is, to be understood that within the scopeof my invention Wide deviations may be made without departing from itsspirit.

Claims 1. A substantially homogeneous, malleable i and ductile goldalloy containing by Weight about 58% gold, 8% copper, 3% magnesium,

5% zinc, and the remainder silver.

2. A substantially homogeneous, malleable and ductile gold alloycontaining by Weight about 58% gold, 3% magnesium, 5% zinc, and

the rel'i'iainder consisting of a metal of the group comprising silverand copper.

3. A substantially homogenous malleable and ductile gold alloycontaining by Weight about 58% gold, 8% copper, 3% aluminum, 3%magnesium, 5% zinc, and the remainder silver.

4. A substantially homogeneous malleable and ductile gold alloycontaining by Weight about 58% gold, 3% magnesium, 3% aluminum, zinc,and the remainder consisting of metal of the group comprising silver andcopper.

5. A substantially homogeneous, malleable and ductile gold alloy havingby Weight from 25 to 85% gold, from 1 to 5% magnesium, the remainderpredominately metal of the group comprising silver and copper.

(5; A substantially homogeneous, malleable an ductile gold alloy havingby weight from 25 to 85% gold, from 1 to 5% mag-- nesium, a small butsubstantial amount of zinc, the remainder predominately metal of thegroup comprising silver and copper.

.7. A substantially homogeneous,malleable' and ductile gold alloy havingby Weight from 25 to 85% gold, to 5% metal of the group comprisingmagnesium, calcium and lithium, the remainder predominately metal of thegroup comprising silver and copper.

8. A substantially homogeneous, malleable and ductile gold alloy havingby Weight from 25 to 85% gold, to metal of the group comprisingmagnesium, calcium and lithium, a small but substantial amount of zinc,the

remainder predominately metal of the group comprising silver and copper.

9. A substantially homogeneous, malleable and ductile gold alloy havingby Weight from 25 to 85% gold, from 1 to 5% magnesium, a

substantial amount of aluminum up to 3%, a small but substantial amountof zinc, the remainder predominately metal of the group comprisingsilver and copper.

In testimony whereof, I have signed my name to this specification.

VICTOR D. DAVIGNON.

